Carpets are typically formed by tufting yarn into a backing and then applying a polymeric coating on the back side of the backing to lock the tufts of yarn and the backing together. The terms “tuft”, “tufting”, “tufted”, and “tufted-in” refer to the process of yarn being inserted into the backing. The backing may be referred to as a carpet backing. The majority of broadloom carpet, including patterned carpet, is manufactured on tufting equipment.
The process of tufting carpet generally consists of feeding the carpet backing through tufting equipment where yarn is then tufted into the carpet backing by one or two rows of needles. Tufting equipment typically contains five hundred (500) to twenty-five hundred (2500) needles across the width of the machine, depending on width of the carpet and gauge of the machine. Gauge refers to the spacing between the needles. For example, one-twelfth ({fraction (1/12)}) gauge means there are twelve (12) needles per inch across the width. If a carpet is tufted twelve (12) feet wide on a one-twelfth ({fraction (1/12)}) gauge machine, there are one thousand seven hundred twenty-eight (1728) needles across the width of the carpet.
Patterns may be formed in carpets in various ways such as by using yarn textures (e.g., loop, sheared loop, cut), yarn color, and more recently, pile height. Historically, patterns on carpets were manufactured by using different color yarns and shifting the needle bars in tufting machines. Depending on color placement of the yarn and shift sequence of the needle bars, manufacturers could create patterns or overall textures.
With the use of servo-motors and/or pneumatic valves in the yarn feed systems of tufting machines, manufacturers are able to create patterns with pile height variation. Using pile height variation, patterns may be created without shifting the needle bars, and the yarn may be tufted into the backing in straight lines or rows.
Carpets are often designed with a repeating design or pattern. For example, across the width of a patterned carpet, a pattern may repeat one or more times.
It is often desirable to join two or more sheets of carpet along a seam in order to cover a desired area. Along each edge of the patterned carpet, manufacturers usually “tuft-in” extra ends (i.e., rows) of yarn, to permit installers to trim back the edges to form a good quality seam between the sheets of carpet. Installers must carefully identify where the last pattern repeat falls near the trim edge of the carpet, and then cut the carpet between ends of yarn to get the pattern to match at seams on the face of the carpet. Installers cut from the top side of the carpet since the patterns are not visible from the back side of the carpet. Trimming the carpet can be difficult and time-consuming, since it is often difficult to identify exactly where a pattern repeats. Moreover, the thickness of the carpet and backing, the gauge of the machine, the type of yarn, and the size of the yarn often causes unintended cross cuts between rows of carpet yarn, which may create an unacceptable pattern match.
The extra ends of yarn tufted into the backing (often referred to as the trim edge) permit installers to cut back the edges of the carpet that may have been damaged during transit to the job site, or to eliminate any manufacturing inconsistencies that may occur at the edges of the carpet. On patterned carpet, the extra ends of yarn are trimmed off between specific rows of yarn near the edge of each sheet of carpet being joined together so that the patterns match when the two sheets of carpet are installed on a floor side by side. This is often referred to as sidematching. If the trimming is performed between the wrong rows, there will be a mismatch in the pattern when the two sheets of carpet are joined together.
On patterned carpet, if a carpet manufacturer does not tuft the extra ends into a carpet for cutting back, the installer would most all of the time be required to trim a full pattern repeat (e.g., six inches, one foot or more depending on the pattern size) in order to get the patterns to match up on the face of the carpet at the seam. Trimming back more than an inch or so on each edge is wasteful, expensive and considered unacceptable by the trade. Therefore, additional tuft rows are usually included on both edges of patterned carpets. Furthermore, with patterned carpet there is an additional requirement that the carpet edge be trimmed back to achieve a pattern match when the carpet is seamed. On some carpets, it is difficult to identify exactly where a pattern repeats due to the subtlety of patterns. Furthermore, once an installer locates the rows of yarn to cut between, it can be difficult to cut between the rows of yarn because the rows are close together. This is especially true on tufting, equipment with gauges ranging from {fraction (1/10)} to {fraction (1/20)} of an inch, which is typical of new patterned tufting equipment.